Fracture-label cytochemistry revealed that T cells are heterogeneous with respect to the expression of transmembrane proteins. It is now important to study lymphocyte populations in T cell leukemias. Preliminary findings indicate that with patients suffering from Micosis fungoids the T cells are homogeneous. The results of this study can therefore lead to the classification, diagnostic and therapeutic assessment of T cell leukemias. The work should also be expanded LS B cells and B-cell leukemia. At present this project is suspended to lack of personnel and laboratory conditions.